// Loop over each element in the object.
for(auto iter = obj.cbegin(); iter != obj.cend(); ++iter)
{
// Make sure to get the value as const reference otherwise you will end up copying
// the whole JSON value recursively which can be expensive if it is a nested object.
const json::value &str = iter->first;
const json::value &v = iter->second;

This topic contains information for the C++ REST SDK 1.0 (codename "Casablanca"). If you are using a later version from the Codeplex Casablanca web page, then use the local documentation at http://casablanca.codeplex.com/documentation.

Taking a look at the changelog for version 2.0.0, you'll find this:

Breaking Change - Changed how iteration over json arrays and objects is performed. No longer is an iterator of std::pair returned. Instead there is a separate iterator for arrays and objects on the json::array and json::object class respectively. This allows us to make performance improvements and continue to adjust accordingly. The array iterator returns json::values, and the object iterator now returns std::pair.

I checked the source on 2.6.0 and you're right, there are no iterator methods at all for the value class. It looks like what you'll have to do is grab the internal object representation from your value class: